As taught in U.S. Pat. No. 3,470,400, to Leon Weisbord and in U.S. Pat. No. 3,479,536 to Frank G. Norris, the vibrating beam accelerometer comprises a thin elongated piezoelectric vibrating beam member mounted to receive compressive tensile forces along its length. The force applied to the beam affects its natural frequency of vibration. The beam is driven by electric fields acting transversely of the beam by means of longitudinally spaced electrodes along the length of the beam. The change in the natural frequency of vibration is detected by appropriate circuitry which derives information therefrom to determine the acceleration on the device.
In the vibrating beam accelerometer of the prior art there is a problem of maintaining the stability of the instrument (e.g. bias and scale factor) because of unwanted temperature variations. In order to achieve stable bias, scale factor and other characteristics, it was necessary in the prior art to maintain a precise temperature control and an extremely low and matched temperature coefficient for the resonant frequency of the beam pairs. These requirements necessitate the use of extreme thermal shielding and equalization, two stage temperature control, and also cause the instrument to be subject to the differential heating effects caused by nuclear radiation. In addition, it is impossible to trim bias and thermal match the instrument once it is assembled.